This proposal is in response to three very exciting and recent findings. The most described six distinct mutations in the intermediate filament protein, GFAP that cause Alexander's disease. The GFAP mutations disrupt intermediate filament organization in astrocyte and also cause the formation of protein inclusions called Rosenthal Fibres, the main histopathological feature of the disease. The inclusions comprise GFAP as well as protein chaperones including, alphabeta-crystallin. Data from my lab identified alphabeta-crystallin as an important intermediate filament associated protein and when mutated it also causes diseases typified by filament inclusions. The second exciting finding is therefore- intermediate filaments require alphabeta-crystallin to function efficiently and without mishap by preserving the individuality of intermediate filaments within filament networks. The formation of intermediate filament networks in cells is an important question and leads es to the third exciting finding-the cytoplasmic spacing of GFAP filaments in astrocytes is set by vimentin. So, other intermediate filament proteins determine a key aspect of the GFAP network. Alexander's disease, like other human diseases caused by mutated intermediate filament proteins. This research programme will establish how GFAP forms networks via Specific Aim 1: To determine the influence of specific GFAP mutations (R79C, R79H, R239H, R239C, and R416W) upon the structural characteristics and properties of GFAP filaments in vitro. Specific Aim 2; To determine the effect of the GFAP mutations upon filament associations and network formation in cells and tissues. Specific Aim 3: To determine the role of associated proteins, including chaperones in GFAP function in astrocytes. The long-term aim of this research is to identify feasible therapeutic strategies that can restore intermediate filament networks in diseased cells.